Method of assembling laminated magnetic cores



March 27,1934.

7 J. c. GRANFIELD 1,952,917

IIETHOD 0F ASSEMBLING LAMINATED MAGNETIC CORES Filed June 9,1930

Inventon:

Jo n C. GPQnFIeId, m His Abtowne Patent ed Mar. 27, 1934 METHOD OF ASSEMBLING LAMINATED MAGNETIC comes .John 0. 'Granfield, Pittsfield, Mass., assignor to General Electric Company, a corporation of New York Application June 9, 1930, Serial No. 459,946

1 Claim. (01. 29-84) My invention relates to laminated magnetic cores such as are used in transformers and reactors, and its general object is to provide anim-f tions tightly together by means of bolts, but the necessary holes for the bolts reduce the effective cross section of the core and are therefore objectionable. The general object of the invention is to provide an improved method of assembling a magnetic core with its'laminations held tightly together but without the necessity of any bolts through them.

The invention will be better understood from the following description taken in connection shows a partial assembly in accordance with the invention of a transformer core, Fig. 2 shows a top .view of the partially assembled core, Fig. 3'

shows the completed core with its clamps and windings, and Fig. i is an explanatory view of a few of the core laminations.

Like reference characters indicate similar parts in the different figures of the drawing.

The invention will be explained in connection with the assembly of a transformer core but it will be apparent that the method may be used in the assembly of cores of other forms of electrical induction apparatus such, for example, as reactors. The core is shown as having two wind- ;ing legs 10 and '11 connected at their ends by two yokes 12 and 13, each winding leg being surrounded by two windings 14 and 15'. The layers or laminations of the core are secured together by clamps 16 and bolts 1'7. The bolts 17 engage notches 18 in the outer edges of the winding legs 10 and 11 to prevent displacement of the clamps 16 on the core. As indicated in Fig. 4, part of the lamination sections in each winding leg extend the full length of the core and the notches 18 in these sections engage the bolts 17 of both the top and bottom clamps and thus tie both sets of clamps together. Other lamination sections in the winding legs are shorter, the yoke sections extending to the outer edges of the core and having notches 18 which are engaged by the bolts 1'7.

with the accompanying drawing in which Fig. 1

Thus, all the lamination sections in the entire core are -clamped rigidly together by the clamps 16 and bolts 17 and the complete transformer may be lifted and supported by means of the 'rods 19 extending from the top clamps. A layer of insulation 20 is usually desirable between each clamp 16 and the core to reduce losses due to stray currents which would otherwise be induced in the clamps.

The lamination sections for each of the winding legs 10 and 11, having been cut or punched accurately to size and dimensions, are laid loosely together, preferably in a horizontal position. The

bottom yoke 12 may usually be built up loosely at the same time with the winding legs, the lamination sections of the yoke being interleaved with those of the winding legs at the lower corners of the core. After the lamination sections have been laid together, they are clamped tightly and compactlyv by the bottom core clamps 16 and anumher of temporary clamps 21 distributed along the winding legs 10 and '11; Each of the temporary ,clamps 21 includes a pair of bars which are clamped against the twofaces of a winding leg of the core by a pair of bolts. If the lamination sections of the winding legs 10 and 11 and the yoke 12 are laid together in a horizontal position, one of the bars of each clamp 21 and one of the clamps 16 may be first laid in position on a suitable horizontal support, the winding legs and yoke being laid upon these clamps, and then the other bars of the clamps 21 and the other clamp 16 laid in place on the winding legs and yoke and the bolts tightened.

It will often be found desirable to interposea temporary rigid metal bar 22 between each face of each winding leg and the temporary clamps 21. These bars 22 support the lamination sections between the clamps 21 so that the clamps may be spaced farther apart and not so many clamps are necessary to prevent undue bulging of the lamination sections.

With the assembled lamination sections of the winding legs tightly clamped together and preferably with the winding legs in vertical position, an insulating cylinder 23 is forced down over each winding leg, the cylinders 23 preferably fitting the winding legs snugly. These cylinders 23 serve not only to insulate the winding legs from the surrounding windings 15 but also serve as smooth rigid supports for the windings. The. windings 15 may, if desired, be formed on the cylinders 23 before the cylinders are forced onto the winding legs as indicated in Figs. 1 and 2. The clamps 21 are of course progressively removed from each winding leg as the cylinder 23 advances, any remaining clamps and the cylinder always holding the lamination sections tightly and compactly together at all points. If desired, a number of small wood rods 24 may be provided along the surfaces of the winding legs to prevent the edges of the lamination sections from scratching and injuring the inner surfaces of the insulating cylinders'23.

After the insulating cylinders 23 have been forced into position and the temporary clamps 21 removed, the temporary supporting bars 22 are pulled out from between the winding legs and cylinders, the topyoke 13 is assembled'and the top core clamps 16 applied as indicated in Fig. 3.

The method which has been described provides a magnetic core with its laminations held tightly and compactly together in its winding legs and therefore with a maximum amount of magnetic material in the available space within the windings. The core is'a'lso strong and rigid without the necessity of any bolts and bolt holes to re:

duce'the effective cross section of the winding legs.

The invention has been explained by describing and illustrating its application in the assembly of a particular form of transformer core but it will be apparent that changes and other applications may be made without departing from the spirit of the invention or the scopevof the appended claim.

What I claim as new'and desire to secure by Letters Patent of the United States is:

The method of assembling a laminated magnetic core winding leg with an insulating cylinder, said method including the steps of applying clamping pressure at spaced intervals along said winding leg, applying additional supporting pressure between said intervals, forcing the insulating cylinder onto the winding leg, progressively removing said clamping pressure as the cylinder advances onto the winding'leg, and finally removing said supporting pressure.

JOHN C. GRANFIELD. 

